Battery case and preparation method therefor, secondary battery assembled therefrom, and electric device

Abstract

Provided in the present application are a battery case and a preparation method therefor, a secondary battery assembled therefrom, and an electric device. The battery case comprises a shell, wherein at least part of a surface of the shell is provided with an insulating protective layer; and the bending fracture angle of the insulating protective layer is 20-60°, and the anti-impact height thereof is 0.2-2 m. The preparation method therefor comprises: coating at least part of a surface of a shell with a resin prepolymer coating, and then subjecting same to cross-linking and curing, wherein the resin prepolymer coating comprises a prepolymer and a toughening agent. The present application solves the problem of an insulating layer on a battery case being prone to cracking and falling off.

Description

Battery shell and preparation method thereof, secondary battery composed thereof, and electrical device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of the following patent applications, the entire contents of which are incorporated herein by reference:

[0003] A Chinese patent application entitled “A battery casing, a preparation method thereof, a secondary battery, and an electrical device”, with application number 202311013586.0, submitted to the State Intellectual Property Office of China on August 14, 2023. Technical Field

[0004] The present application relates to the field of battery technology, and in particular to a battery casing and a preparation method thereof, a secondary battery composed thereof, and an electrical device. Background Art

[0005] The battery casing primarily protects the battery cells, preventing external oxygen and moisture from coming into contact with the electrolyte, electrodes, and other materials within the battery. Because the battery casing is in constant contact with the electrolyte and the live cells, its corrosion resistance and insulation properties are crucial to the battery's lifespan and safety. Typically, a corrosion-resistant insulating layer is added to the battery casing to improve its corrosion resistance and prevent short circuits. However, this insulating layer is prone to cracking and detachment, thus losing its insulating properties.

[0006] To this end, the present invention is proposed.

[0007] Summary of the Invention

[0008] The present application is made in view of the above-mentioned problems, and its purpose is to provide a battery casing and its preparation method, a secondary battery composed of the components, and an electrical device, which solves the problem that the insulating layer on the battery casing is prone to cracking and falling off.

[0009] In order to achieve the above objectives, this application provides the following technical solutions.

[0010] A first aspect of the present application provides a battery housing, comprising a shell, at least a portion of the surface of the shell being provided with an insulating protective layer;

[0011] The insulating protective layer has a bending and breaking angle of 20° to 60° and an impact-resistant height of 0.2 to 2 m.

[0012] Therefore, the insulating protective layer on the battery shell of the present application exhibits greater toughness due to its high bending strength and impact strength. It is not easy to crack or fall off after the shell expands and contracts during the use of the battery, thus exhibiting more lasting corrosion resistance and insulation.

[0013] In any embodiment, the shear force between the insulating protective layer and the shell is ≥5 MPa, preferably ≥7 MPa.

[0014] As the shear force increases, the connection force between the insulating protective layer and the shell increases, making it less likely to fall off, and the service life of the battery shell is extended.

[0015] In any embodiment, the insulating protective layer has a bending and fracture angle of 30° to 60° and an impact resistance height of 0.2 to 0.6 m.

[0016] In any embodiment, the insulation protection layer has a resistance of ≥1 GΩ under conditions of DC withstand voltage, voltage of 1000V, and 5s. Higher resistance improves the insulation performance of the housing.

[0017] In any embodiment, the resistance of the insulating protective layer under the conditions of DC withstand voltage, voltage of 1000V, and 5s is ≥5GΩ.

[0018] In any embodiment, the thickness of the insulating protective layer is 1 to 1000 μm.

[0019] Since the insulating protective layer of the present invention has stronger toughness, its thickness on the shell is not easily limited and can be arbitrarily adjusted within a wide range of 1 to 1000 μm.

[0020] In any embodiment, the inner wall of the shell is provided with the insulating protective layer.

[0021] Preferably, both the inner wall and the outer wall of the shell are provided with the insulating protective layer.

[0022] After the inner and outer walls are provided with insulating protective layers, the battery casing has a longer service life and higher safety.

[0023] In any embodiment, the insulating protective layer is a resin protective layer.

[0024] In any embodiment, the insulating protective layer comprises at least one of the following: phenolic resin, polyimide, epoxy resin, urea-formaldehyde resin, polyetheretherketone, and polybenzimidazole resin. The above resins may be any one or a combination thereof, such as a combination of phenolic resin and polyimide, or a combination of epoxy resin and urea-formaldehyde resin.

[0025] In any embodiment, the insulating protective layer further comprises a toughening agent: at least one of natural rubber, nitrile rubber, styrene-butadiene rubber, nylon, bismaleimide, glass fiber, polyurethane, aluminum oxide, magnesium oxide, calcium oxide, and barium oxide.

[0026] In any embodiment, the shell includes at least one of the following: an aluminum shell, an aluminum alloy shell, and a steel shell.

[0027] A second aspect of the present application further provides a method for preparing a battery housing, comprising:

[0028] Applying a resin prepolymer coating on at least a portion of the surface of the shell, and then cross-linking and curing it;

[0029] The resin prepolymer coating comprises a prepolymer and a toughening agent;

[0030] The prepolymer comprises at least one of the following: phenolic resin, polyimide, epoxy resin, urea-formaldehyde resin, polyetheretherketone, polybenzimidazole resin;

[0031] The toughening agent includes at least one of the following: natural rubber, nitrile rubber, styrene-butadiene rubber, nylon, bismaleimide, glass fiber, polyurethane, aluminum oxide, aluminum oxide, magnesium oxide, calcium oxide, and barium oxide.

[0032] The resin prepolymer used in this application, after cross-linking with a toughening agent, produces a more flexible resin with higher flexural strength and impact resistance. Furthermore, because this application employs a coating-first, then cross-linking method to form the protective layer, i.e., an in-situ polymerization method, the resin is stably chemically bonded to the shell surface, creating a strong bond between the two and making the protective layer less likely to fall off.

[0033] In any embodiment, in the resin prepolymer coating, the weight ratio of the prepolymer is 60 to 99.9%, including but not limited to 60%, 65%, 67%, 70%, 73%, 75%, 80%, 83%, 85%, 90%, 95%, 99%, etc., preferably 80 to 99%.

[0034] Keeping the prepolymer content within the above reasonable range can achieve a balanced toughening effect and crosslinking degree. If the prepolymer content is too low, less than 60%, the toughening agent is too high, making it difficult to crosslink and form a polymer insulation layer. If it is higher than 99.9%, the toughening agent is too low, and the toughening effect is limited.

[0035] In any embodiment, the particle size of the toughening agent is 0.1 to 10 μm, preferably 0.2 to 3 μm.

[0036] Controlling the particle size of the toughening agent within the above range can improve the toughness consistency of each area of ​​the insulation protective layer. If the particle size is less than 0.1μm, it is easy to agglomerate and difficult to disperse, resulting in poor toughening effect. If it is greater than 10μm, the uniformity is poor.

[0037] The particle size in this application refers to the average particle size.

[0038] In any embodiment, the prepolymer includes at least one of phenolic resin, urea-formaldehyde resin, and polybenzimidazole, and the toughening agent includes at least one of nitrile rubber, styrene-butadiene rubber, nylon, and polyurethane. This combination can achieve a good synergistic effect, and the resulting protective insulating layer has excellent bending strength, impact strength, bonding strength with the housing, and insulation properties.

[0039] In any embodiment, the molecular weight of the resin prepolymer is 100 to 50,000, preferably 400 to 2,000.

[0040] Keeping the molecular weight within the above reasonable range can balance processability and electrolyte resistance. If the molecular weight is <100, it is difficult to polymerize and cross-link to form a polymer, and the electrolyte resistance is poor. If the molecular weight is >50,000, it is difficult to dissolve, has high viscosity, and is difficult to process.

[0041] The molecular weight in this application refers to the average molecular weight.

[0042] In any embodiment, the cross-linking and curing comprises: reacting at 25° C. to 300° C. for 5 to 500 minutes.

[0043] If the curing temperature is too low, the curing time will be too long. If the curing temperature is too high, the shell will be easily damaged. Controlling the curing temperature and time within the above range can achieve a good balance between economic benefits and product quality.

[0044] In any embodiment, the cross-linking and curing reaction further comprises: adding a curing agent;

[0045] The curing agent preferably includes at least one of the following: hexamethylenetetramine, ethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, p-phenylenediamine, m-phenylenediamine, terephthalic acid, terephthalic acid, maleic anhydride, phthalic anhydride.

[0046] Adding a curing agent helps to improve the reaction efficiency.

[0047] In any embodiment, before the coating, the shell surface is further subjected to activation treatment: the shell surface is subjected to at least one of laser cleaning, plasma cleaning, and acid cleaning.

[0048] Laser cleaning, plasma cleaning, acid cleaning, and other methods can create a surface rich in reactive groups like -OH, -C=O, O·, and -COOH, creating a rougher surface with a larger surface area. These reactive groups facilitate covalent bonding with the prepolymer, and the roughened surface promotes mechanical interlocking between the polymer and the shell. Therefore, these activation treatments can enhance the shear force between the insulating layer and the shell both chemically and physically.

[0049] A third aspect of the present application provides a secondary battery, comprising the battery housing of the first aspect of the present application or the battery housing prepared according to the method of the second aspect of the present application.

[0050] A fourth aspect of the present application provides an electrical device comprising the secondary battery according to the third aspect of the present application.

[0051] In summary, compared with the prior art, this application achieves the following technical effects:

[0052] (1) By adding a toughening agent, the flexibility of the insulating protective layer is improved, and the insulating protective layer has higher bending strength and impact strength, so that the insulating protective layer will not crack or break under large deformation, and the insulating layer structure is kept stable. As a result, the battery cell contained in the battery shell does not need to be wrapped with an insulating layer.

[0053] (2) The insulating protective layer is formed by in-situ polymerization, which improves the bonding strength between the protective layer and the shell, and the shear force between the two is greater.

[0054] (3) Activating the shell surface before in-situ polymerization can further increase the shear force between the insulating protective layer and the shell. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] FIG1 is a schematic diagram of a secondary battery according to an embodiment of the present application.

[0056] FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .

[0057] FIG3 is a schematic diagram of a battery module according to an embodiment of the present application.

[0058] FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0059] FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present application.

[0060] FIG6 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0061] Explanation of reference numerals: 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 secondary battery; 51 outer case; 52 electrode assembly; 53 cover plate. DETAILED DESCRIPTION

[0062] Below, the battery case and its manufacturing method, secondary battery and electrical device of the present application are described in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0063] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0064] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0065] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0066] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0067] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may indicate that other components not listed may also be included or that only the listed components are included.

[0068] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0069] Because battery casings are in constant contact with the electrolyte and the charged cells within, their corrosion resistance and insulation properties are crucial to the battery's lifespan and safety. Typically, to improve these properties, a corrosion-resistant insulation layer, typically made of resin, is added. However, current insulation layers are brittle and have low toughness. As the battery cells expand and contract during use, the battery casing also expands and contracts, causing the insulation layer to deform and become prone to cracking and shedding, ultimately losing its insulating properties.

[0070] In order to improve the toughness of the insulating layer and prevent it from cracking or falling off, the present application provides a battery casing, which includes a shell, at least part of the surface of the shell is provided with an insulating protective layer;

[0071] The insulating protective layer has a bending and breaking angle of 20° to 60° and an impact-resistant height of 0.2 to 2 m.

[0072] Therefore, the insulating protective layer on the battery shell of the present application exhibits greater toughness due to its high bending strength and impact strength. It is not easy to crack or fall off after the shell expands and contracts during the use of the battery, thus exhibiting more lasting corrosion resistance and insulation.

[0073] The bending fracture angle in this application refers to the bending angle of the battery shell when the battery shell is bent by a cylindrical shaft with a diameter of 32 mm until the insulating protective layer breaks, with reference to GB-6742-86. The bending fracture angle in this application can be any value in the range of 20° to 60°. In some embodiments, the bending fracture angle reaches 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, etc., or reaches the range of 30° to 60°, 40° to 60°, 50° to 60°, etc.

[0074] The impact resistance height in this application refers to the reference to GB / T 1732-93, using a 1kg steel ball dropped from a certain height on the battery casing until the insulating protective layer is broken, and the height of the insulating protective layer is recorded. This height is the impact resistance height. The impact strength in this application can be any value in the range of 0.2 to 2m. In some embodiments, the impact strength reaches 0.2m, 0.3m, 0.4m, 0.5m, 0.6m, 0.7m, 0.8m, 0.9m, 1m, 1.5m, 2m, etc., or reaches the range of 0.2 to 0.6m, 0.7m to 1m, 1m to 2m, etc.

[0075] The shell in this application refers to the main body that plays a supporting role, and is preferably made of materials with the characteristics of light weight, low price, easy processing, good mechanical properties or good thermal conductivity, including but not limited to aluminum shell, aluminum alloy shell, steel shell, etc.

[0076] In some embodiments, a high shear force is applied between the insulating protective layer and the housing, for example, ≥5 MPa, preferably ≥7 MPa. As the shear force increases, the connection between the insulating protective layer and the housing increases, making it less likely to fall off, and extending the battery housing's service life.

[0077] At different positions of the shell, the shear force between the protective layer and the shell can be the same or different.

[0078] Generally, as the shear force increases, the connection force between the insulating protective layer and the shell increases, making it less likely to fall off, and the service life of the battery shell is extended.

[0079] The above shear force is obtained by referring to GBT 7124 / ISO 4587 test.

[0080] Since the insulating protective layer of the present application has high toughness, its thickness on the shell is not easily limited and can be adjusted arbitrarily within a wide range of 1 to 1000 μm, including but not limited to 1 to 10 μm, 10 to 100 μm, 100 to 1000 μm, 10 to 50 μm, 50 to 100 μm, 100 to 500 μm, 500 to 1000 μm, etc.

[0081] In the present application, the location and area of ​​the insulating protective layer can be adjusted, for example, the insulating protective layer can be set only on the inner wall of the shell, or only on the outer wall of the shell, or on both the inner and outer walls of the shell.

[0082] In some embodiments, the insulation protection layer has a resistance of ≥1 GΩ under the conditions of DC withstand voltage, voltage of 1000V, and 5s, indicating good insulation properties. In some embodiments, the resistance is also ≥5 GΩ.

[0083] In some embodiments, the insulating protective layer comprises at least one of the following: phenolic resin, polyimide, epoxy resin, urea-formaldehyde resin, polyetheretherketone, and polybenzimidazole resin. These resins easily achieve the above-mentioned properties and can be any one of the above resins or a combination of different resins.

[0084] In some embodiments, the insulating protective layer further includes a toughening agent: at least one of natural rubber, nitrile rubber, styrene-butadiene rubber, nylon, bismaleimide, glass fiber, polyurethane, aluminum oxide, magnesium oxide, calcium oxide, and barium oxide.

[0085] There are many methods for preparing the battery casing having the above-mentioned insulating protective layer characteristics of the present application. The present application provides a preparation method with a simple process and readily available raw materials, which includes:

[0086] Applying a resin prepolymer coating on at least a portion of the surface of the shell, and then cross-linking and curing it;

[0087] The resin prepolymer coating comprises a prepolymer and a toughening agent;

[0088] The prepolymer comprises at least one of the following: phenolic resin, polyimide, epoxy resin, urea-formaldehyde resin, polyetheretherketone, polybenzimidazole resin;

[0089] The toughening agent includes at least one of the following: natural rubber, nitrile rubber, styrene-butadiene rubber, nylon, bismaleimide, glass fiber, polyurethane, aluminum oxide, aluminum oxide, magnesium oxide, calcium oxide, and barium oxide. The resin prepolymer used in this application, after cross-linking with the toughening agent, produces a more flexible resin, exhibiting higher flexural strength and impact resistance. Furthermore, because this application employs a coating-first, then cross-linking method to form the protective layer, i.e., an in-situ polymerization method, the resin is stably chemically bonded to the shell surface, resulting in a strong bond between the two and making the protective layer less likely to fall off.

[0090] The coating in this application includes but is not limited to spraying, smearing, dipping and other means.

[0091] The cross-linking curing in this application includes but is not limited to thermal curing, UV curing and other means.

[0092] The above-mentioned resin prepolymer coating used in this application contains a toughening agent, so the resulting protective layer has good toughness, its bending and fracture angle can reach at least 20° to 60°, and its impact resistance height can reach at least 0.2 to 2m.

[0093] On this basis, the prepolymer type and content, toughening agent type and content, cross-linking and curing conditions, surface activation treatment, etc. can be adjusted to further improve the toughness and insulation of the insulating protective layer itself, or improve the shear force between the insulating protective layer and the shell, as listed below.

[0094] In some embodiments,

[0095] In any embodiment, in the resin prepolymer coating, the weight ratio of the prepolymer is 60-99.9%, and can be 80-99%, 80-95%, or 90-95%.

[0096] Keeping the prepolymer content within the above reasonable range can achieve a balanced toughening effect and crosslinking degree. If the prepolymer content is too low, less than 60%, the toughening agent is too high, making it difficult to crosslink and form a polymer insulation layer. If it is higher than 99.9%, the toughening agent is too low, and the toughening effect is limited.

[0097] In some embodiments, the particle size of the toughening agent is 0.1 to 10 μm, and can be 0.2 to 3 μm.

[0098] Controlling the particle size of the toughening agent within the above range can improve the toughness consistency of each area of ​​the insulation protective layer. If the particle size is less than 0.1μm, it is easy to agglomerate and difficult to disperse, resulting in poor toughening effect. If it is greater than 10μm, the uniformity is poor.

[0099] The particle size in this application refers to the average particle size.

[0100] In some embodiments, the molecular weight of the prepolymer is 100-50,000, including but not limited to 100, 500, 1,000, 3,000, 5,000, 10,000, 20,000, 30,000, 40,000, 50,000, etc., and can also range from 400-2,000, 2,000-5,000, etc.

[0101] Keeping the molecular weight within the above reasonable range can balance processability and electrolyte resistance. If the molecular weight is <100, it is difficult to polymerize and cross-link to form a polymer, and the electrolyte resistance is poor. If the molecular weight is >50,000, it is difficult to dissolve, has high viscosity, and is difficult to process.

[0102] The molecular weight in this application refers to the average molecular weight.

[0103] In some embodiments, the prepolymer includes at least one of phenolic resin, urea-formaldehyde resin, and polybenzimidazole, and the toughening agent includes at least one of nitrile rubber, styrene-butadiene rubber, nylon, and polyurethane. This combination can achieve a good synergistic effect, resulting in a protective insulating layer with excellent flexural strength, impact strength, bonding strength with the housing, and insulation properties.

[0104] In some embodiments, cross-linking and curing includes reacting at 25° C. to 300° C. for 5 to 500 minutes.

[0105] If the curing temperature is too low, the curing time will be too long. If the curing temperature is too high, the shell will be easily damaged. Controlling the curing temperature and time within the above range can achieve a good balance between economic benefits and product quality.

[0106] In some embodiments, the cross-linking and curing reaction further comprises: adding a curing agent. Adding a curing agent helps to improve the reaction efficiency.

[0107] The curing agent may include at least one of hexamethylenetetramine, ethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, p-phenylenediamine, m-phenylenediamine, terephthalic acid, terephthalic acid, maleic anhydride, and phthalic anhydride.

[0108] In some embodiments, the shell surface is further activated before coating: the shell surface is subjected to at least one of laser cleaning, plasma cleaning, and acid cleaning.

[0109] Laser cleaning, plasma cleaning, acid cleaning, and other methods can create a surface rich in reactive groups like -OH, -C=O, O·, and -COOH, creating a rougher surface with a larger surface area. These reactive groups facilitate covalent bonding with the prepolymer, and the roughened surface promotes mechanical interlocking between the polymer and the shell. Therefore, these activation treatments can enhance the shear force between the insulating layer and the shell both chemically and physically.

[0110] The battery casing and the battery casing obtained by the preparation method described above in this application can be used for any type of battery, including but not limited to lithium batteries, sodium batteries, etc.

[0111] In addition, the secondary battery, battery module, battery pack, and electric device of the present application will be described below with reference to the drawings as appropriate.

[0112] In one embodiment of the present application, a secondary battery is provided.

[0113] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0114] [Positive electrode]

[0115] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes the positive electrode active material of the first aspect of the present application.

[0116] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0117] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0118] In some embodiments, when the secondary battery is a lithium-ion battery, the positive electrode active material may adopt the positive electrode active material for lithium-ion batteries known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0119] In some embodiments, when the secondary battery is a sodium ion battery, the positive electrode active material may be a positive electrode active material for sodium ion batteries known in the art. As an example, the positive electrode active material may be used alone or in combination of two or more. Among them, the positive electrode active material may be selected from sodium iron composite oxide (NaFeO2), sodium cobalt composite oxide (NaCoO2), sodium chromium composite oxide (NaCrO2), sodium manganese composite oxide (NaMnO2), sodium nickel composite oxide (NaNiO2), sodium nickel titanium composite oxide (NaNiO2), etc. 1 / 2 Ti 1 / 2 O2), sodium nickel manganese composite oxide (NaNi 1 / 2 Mn 1 / 2 O2), sodium iron manganese composite oxide (Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2), sodium nickel cobalt manganese composite oxide (NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2), sodium iron phosphate (NaFePO4), sodium manganese phosphate (NaMn P O4), sodium cobalt phosphate compounds (NaCoPO4), Prussian blue materials, polyanion materials (phosphates, fluorophosphates, pyrophosphates, sulfates), etc., but the present application is not limited to these materials. The present application can also use other traditionally known materials that can be used as positive electrode active materials for sodium ion batteries.

[0120] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0121] In some embodiments, the positive electrode film layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0122] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0123] [Negative electrode]

[0124] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0125] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0126] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0127] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0128] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0129] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0130] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0131] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0132] [Electrolytes]

[0133] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0134] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0135] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0136] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0137] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0138] [Isolation film]

[0139] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0140] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0141] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0142] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0143] In some embodiments, the outer packaging of the secondary battery may be the battery housing described above in this application.

[0144] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square, or any other shape. For example, FIG1 shows a secondary battery 5 with a square structure as an example.

[0145] In some embodiments, referring to Figure 2, the battery casing may include an outer shell 51 and a cover plate 53. The outer shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The outer shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs. Both the outer shell 51 and the cover plate 53 can adopt the structure of the battery casing described above.

[0146] In some embodiments, secondary batteries can be assembled into a battery module. The number of secondary batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0147] Figure 3 shows an example battery module 4. Referring to Figure 3 , within the battery module 4, multiple secondary batteries 5 may be arranged sequentially along the length of the battery module 4. Of course, any other arrangement is also possible. Furthermore, the multiple secondary batteries 5 may be secured together using fasteners.

[0148] Optionally, the battery module 4 may further include a housing having a receiving space, wherein the plurality of secondary batteries 5 are received in the receiving space. The housing may be the battery housing of the present application.

[0149] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0150] Figures 4 and 5 illustrate an example battery pack 1. Referring to Figures 4 and 5 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be placed over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0151] In addition, the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0152] As the electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0153] Figure 6 shows an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0154] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0155] Example

[0156] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0157] Examples 1-23

[0158] A battery shell is prepared by the following method:

[0159] S1, cleaning: polish the 500 μm thick aluminum shell on 200#, 500#, 1000#, and 3000# sandpaper in sequence to remove the oxide layer on its surface.

[0160] S2, surface activation: laser cleaning, plasma cleaning or acid cleaning is performed on the surface of the aluminum shell after the treatment in step S1, as shown in Table 1 for details.

[0161] Among them, the laser cleaning process: use laser to clean the surface of the aluminum shell at a power of 200W.

[0162] Plasma cleaning process: Use air or oxygen as the gas source and clean the aluminum shell surface at a cleaning pressure of 10 to 100 Pa.

[0163] The pickling process is to clean the aluminum shell surface with 0.01-5% acid solution, and then rinse with water to remove the residual acid solution. The acid solution includes at least one of hydrochloric acid, folic acid, oxalic acid, nitric acid, sulfuric acid, acetic acid, and citric acid solution.

[0164] S3, applying prepolymer coating: taking prepolymer and toughening agent, mixing them in a solvent, and coating them on the inner and outer surfaces of the activated aluminum shell. The types of resin prepolymer and toughening agent and the ratio of the two are detailed in Table 1.

[0165] S4, cross-linking and curing: referring to the curing conditions in Table 1, to obtain an aluminum shell with an insulating protective layer on the surface.

[0166] Comparative Example

[0167] See Table 1.

[0168] The shear force between the insulating protective layer and the aluminum shell, the thickness and swelling rate of the insulating protective layer, the corrosion resistance, etc. of the products of each embodiment and comparative example were tested. The test method is as follows.

[0169] Insulation shear test: Test standard GBT 7124 / ISO 4587.

[0170] Protective layer thickness: tested using a film thickness tester.

[0171] Bending fracture angle: Refer to GB-6742-86, cut the aluminum shell with an insulating protective layer on the surface into 5*12cm aluminum strips, use a cylindrical shaft with a diameter of 32mm to press and bend the aluminum strips until the insulating protective layer breaks, and record the bending angle of the aluminum strips at the time of rupture.

[0172] Impact resistance height: Refer to GB / T 1732-93. Use a 1kg steel ball to drop from a certain height onto an aluminum sheet coated with an insulating protective layer until the insulating protective layer breaks. Record the height of the insulation protective layer.

[0173] Resistance: Use resistance meter to test, DC withstand voltage, voltage 1000V, 5s conditions.

[0174] The results are shown in Table 1.

[0175] Table 1

[0176] Note: "Polyimide prepolymer" in Table 1 refers to (C4H4N2O) 15The phenolic resin prepolymer with a molecular weight of 1000 refers to HOH2C-(PhOH-CH2)3-[PhOH(CH2OH)CH2]3-CH2OH, the phenolic resin prepolymer with a molecular weight of 2000 refers to HOH2C-(PhOH-CH2)6-[PhOH(CH2OH)CH2]]6-CH2OH, and the phenolic resin prepolymer with a molecular weight of 50000 refers to HOH2C-(PhOH-CH2)150-[PhOH(CH2OH)CH2] 150 -CH2OH, the phenolic resin prepolymer with a molecular weight of 100 is HOH2C-PhOH, and the epoxy resin is epoxy resin E44. The ratio of prepolymer to toughening agent is by mass.

[0177] The results show:

[0178] Compared to Comparative Example 2, which did not include a toughening agent, the shear force, flexural strength, and impact strength of the outer shell and surface protective layer after toughening were significantly improved. Comparing Example 1 with Comparative Example 2, the flexural strength and impact strength of polypropylene methyl ester, used as the insulating protective layer material, were far lower than those of polyimide, epoxy resin, phenolic resin, and the like. Compared to Comparative Example 3, which used non-in-situ polymerization and crosslinking, the shear force, flexural strength, and impact strength of the outer shell after in-situ polymerization in Example 3 were significantly improved. The type, particle size, and amount of toughening agent significantly affected shear force, flexural strength, and impact strength.

[0179] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery casing, characterized in that: It comprises a shell, at least part of the surface of which is provided with an insulating protective layer; The insulating protective layer has a bending and breaking angle of 20° to 60° and an impact resistance height of 0.2m to 2m.

2. The battery housing according to claim 1, characterized in that: The shear force between the insulating protective layer and the shell is ≥5MPa.

3. The battery housing according to claim 2, characterized in that: The shear force between the insulating protective layer and the shell is ≥7MPa.

4. The battery casing according to any one of claims 1 to 3, characterized in that: The bending and breaking angle of the insulating protective layer is 30° to 60°, and the impact resistance height is 0.2m to 0.6m.

5. The battery housing according to any one of claims 1 to 3, characterized in that: The insulation protection layer has a resistance of ≥1GΩ under the conditions of DC withstand voltage, voltage 1000V, and 5s.

6. The battery casing according to any one of claim 5, characterized in that: The resistance of the insulating protective layer under the conditions of DC withstand voltage, voltage 1000V, 5s is ≥5GΩ.

7. The battery casing according to any one of claims 1 to 3, characterized in that: The thickness of the insulating protection layer is 1 to 1000 μm.

8. The battery casing according to any one of claims 1 to 3, characterized in that: The inner wall of the shell is provided with the insulating protective layer.

9. The battery casing according to claim 8, characterized in that: The inner wall and the outer wall of the shell are both provided with the insulating protective layer.

10. The battery casing according to any one of claims 1 to 3, characterized in that: The insulating protective layer includes at least one of the following: phenolic resin, polyimide, epoxy resin, urea-formaldehyde resin, polyetheretherketone, and polybenzimidazole resin.

11. The battery housing according to claim 10, characterized in that: The insulating protective layer also includes a toughening agent: at least one of natural rubber, nitrile rubber, styrene-butadiene rubber, nylon, bismaleimide, glass fiber, polyurethane, aluminum oxide, magnesium oxide, calcium oxide, and barium oxide.

12. The battery casing according to any one of claims 1 to 3, characterized in that: The shell includes at least one of the following: an aluminum shell, an aluminum alloy shell, and a steel shell.

13. A method for preparing a battery shell, characterized in that: include: Applying a resin prepolymer coating on at least a portion of the surface of the shell, and then cross-linking and curing it; The resin prepolymer coating comprises a prepolymer and a toughening agent; The prepolymer comprises at least one of the following prepolymers: phenolic resin, polyimide, epoxy resin, urea-formaldehyde resin, polyetheretherketone, polybenzimidazole resin; The toughening agent includes at least one of the following: natural rubber, nitrile rubber, styrene-butadiene rubber, nylon, bismaleimide, glass fiber, polyurethane, aluminum oxide, magnesium oxide, calcium oxide, and barium oxide.

14. The preparation method according to claim 13, characterized in that: In the resin prepolymer coating, the weight ratio of the prepolymer is 60 to 99.9%.

15. The preparation method according to claim 14, characterized in that: In the resin prepolymer coating, the weight ratio of the prepolymer is 80-99%.

16. The preparation method according to any one of claims 13 to 15, characterized in that: The particle size of the toughening agent is 0.1 μm to 10 μm.

17. The preparation method according to claim 16, characterized in that: The particle size of the toughening agent is 0.2 μm to 3 μm.

18. The preparation method according to any one of claims 13 to 15, characterized in that: The molecular weight of the prepolymer is 100 to 50,000.

19. The preparation method according to claim 18, characterized in that: The molecular weight of the prepolymer is 400-2000.

20. The preparation method according to any one of claims 13 to 15, characterized in that: The cross-linking and curing comprises: reacting at 25° C. to 300° C. for 5 min to 500 min.

21. The preparation method according to any one of claims 13 to 15, characterized in that: The prepolymer includes at least one of phenolic resin, urea-formaldehyde resin and polybenzimidazole, and the toughening agent includes at least one of nitrile rubber, styrene-butadiene rubber, nylon and polyurethane.

22. The preparation method according to any one of claims 13 to 15, characterized in that: The cross-linking and curing reaction further comprises: adding a curing agent.

23. The preparation method according to claim 22, characterized in that: The curing agent includes at least one of the following: hexamethylenetetramine, ethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, p-phenylenediamine, m-phenylenediamine, terephthalic acid, terephthalic acid, maleic anhydride, and phthalic anhydride.

24. The preparation method according to any one of claims 13 to 15, characterized in that: Before the coating, the shell surface is also activated: the shell surface is at least one of laser cleaning, plasma cleaning and acid cleaning.

25. A secondary battery, characterized in that: A battery shell comprising the battery shell according to any one of claims 1 to 12 or a battery shell prepared according to the preparation method according to any one of claims 13 to 24.

26. An electrical device, characterized in that: Includes the secondary battery as claimed in claim 25.

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